1) Mean
The mean is given by the sum of the data divided by the number of data (4, in this case):
[tex]\mu = \frac{1}{N} \sum x_i = \frac{1}{4}(72.42+91.50+58.99+69.02) = \frac{291.93}{4}=72.98 $ [/tex]
2) Standard deviation
The standard deviation is given by:
[tex]\sigma = \sqrt{ \frac{1}{N} \sum (x_i-\mu)^2 } [/tex]
where [tex]\mu[/tex] is the mean, that we already found at point 1), and N=4. Substituting data, we have:
[tex]\sigma = \sqrt{ \frac{1}{4} ((-0.56)^2+(18.52)^2+(-13.99)^2+(-3.96)^2) } =[/tex]
[tex]= \sqrt{ \frac{1}{4} (554.71)} = \sqrt{138.68} =11.78 $[/tex]
